The present invention relates generally to fire barriers and more particularly to fire barriers that can accommodate multi-dimensional joints.
The background information discussed below is presented to better illustrate the novelty and usefulness of the present invention. This background information is not admitted prior art. The particular versions of the invention as described below are provided, in part, as illustrative and exemplary. Thus, the described versions should not be taken as limiting. Additionally, the invention is not limited to the examples provided.
Customarily, buildings were built with static joints. Modern building codes, however, require that building design and construction now take into account factors that can, over time, change the physical dimensions of a structure. These factors include extreme or repetitive changes in temperature, the force of wind impinging on the building, forces due to seismic events, settling of the subsoil, remodeling of the building, or excavation on or near the site, among other factors. To accommodate the stress on the building caused by these factors without compromising the integrity of the building, architects and builders may design the structure in sub-units where the sub-units are meant to remain some small distances away from each other and meet at what is referred to as “expansion joints”.
Expansion joints allow differential building movement to take place without risking damage to the whole structure. These joints represent gaps in the structure which can widen or narrow due to differential movement of adjacent structural units and/or can reduce the stress caused by shear motion of adjacent structural units. Dynamic moveable joints are often referred to in the trade as “construction joints,” “soft joints,” “dynamic voids”, “seismic joints,” and “expansion joints.” Expansion joints or voids often occur where two wall sections, a wall and a floor, or a wall and ceiling meet, for example.
While the presence of these joints improves the integrity of the structure as a whole, they present a major risk to the structure in the event of a fire. The gaps at the joints provide easy pathways for flame, heat, and smoke to spread rapidly throughout the structure by utilizing what is known as the “chimney effect,” that is the updraft created by heated air rising up through the structural gaps. Building codes for commercial structures generally require fire barriers capable of preventing flame and smoke from passing through building joints into adjoining areas. Various fire barrier means are available and include fire retardant and/or intumescent putties, caulks, wraps, and mats.
The fire barrier products mentioned above, although suitable for static joints, are generally not suitable for acting as fire barriers for dynamic joints. To reduce the risk created by the chimney effect due to dynamic joints, a number of attempts have been made to block the joints with fire resistant materials. A fire barrier for a dynamic joint generally needs to be capable of accommodating the complex differential movement of the building structural units and to retain its resiliency over an extended period of time under dynamic conditions. Further, during a fire event, the joint is likely to be subject to even greater movement, thereby making it essential that the fire barrier retains its integrity to prevent the migration of heat, flame, and smoke.
Commonly available are fire resistant materials, such as fire brick, which typically may be either rigid and/or brittle, or fire barrier blankets that are constructed of refractory fibers that are flexible but can be easily damaged.
Rigid and brittle materials have been adapted to sealing building joints while maintaining flexibility. This is accomplished by first creating hollowed out regions within the structural units that meet at a joint that is to be sealed with a fire resistant barrier. The fire resistant barrier, which consists of a thin layer of material of appropriate high-temperature properties, is then inserted into both hollowed gaps at the ends of the adjacent structural units. Thus, the widening or narrowing or shear motion of the adjacent plates is accommodated by the fire resistant barrier moving in a sliding fashion within the adjacent structural units. As long as the lateral dimensions of the barrier exceed the widest distance between the adjacent structural units during differential movement, the integrity of the barrier should remain. Similarly, when the structural units move together, the barrier should remain undamaged providing that the lateral dimension of the barrier is less than the distance between the bottoms of the hollowed out regions of the structural units. The major drawback of this approach is that the fire resistant material must be thin enough to fit within the hollowed out areas of the adjacent structural units. However, fabricating the hollowed out areas further complicates the construction of the building and increases the cost of the construction. Moreover, correct installation of such a barrier in a pre-existing building is difficult and expensive.
On the other hand, fire resistant materials can be fabricated into thin, flexible fibers which can be incorporated into flexible, fire resistant structures resembling a blanket. The advantages of such a material are that the fabrication is not very expensive, the draping of the blanket across a joint is readily accomplished and any differential movement of the adjacent structural units can be accommodated by incorporating an appropriate amount of slack in the blanket during installation. The blanket, however, is mechanically weak and can be easily damaged by tearing or ripping either accidentally or intentionally during or after installation thus largely compromising the integrity of the fire resistant barrier. A number of attempts have been made to protect the blanket from such mechanical damage. These have generally relied on the fabrication of a composite blanket which incorporates the fire resistant material between layers of a stronger, protective material such as metal foils or metal screens. The fire resistant layer can freely move with respect to these protective layers or they may be attached together via threads or similar attaching means.
Given the wide variety of movements that may occur between structural elements in a building, particularly one situated in a seismically active region, there still remains the possibility of gaps appearing in the fire barrier. To reseal these gaps in the event of a fire, intumescent materials are frequently added to the barrier. These are materials that expand when rapidly heated and at the same time have fire resistant properties. Thus, these provide a second method of sealing the structural gap in a building.
Attempts have been made to provide for sealing the dynamic joints that occur between structural units in a building. All of these solutions only provide for a fire barrier that is designed to obstruct air flow through a gap that occurs only between two building structures, such as the gap that occurs at the join of two walls. Many expansion joints, however, occur at the juncture of more than two building structures, such as where four walls meet to create a cross-wise gap, or where two exterior walls and an interior wall meet creating a “T”-shaped gap. Presently, there is no system which is capable of sealing a gap between more than two structural units in a building. None of the previously described fire barrier assemblies is capable of bridging the kind of multi-dimensional gap that occurs at the convergence of a plurality of structural units.
Thus, it is clear that what is sorely lacking in the art is a fire barrier that can accommodate that important safety need. It would be a significant improvement in the art to provide a fire barrier that is designed to provide a multi-pathway air flow obstacle. Ideally, the novel multi-dimensional fire barrier would ideally be constructed as a one piece, ready to install, unit to better ensures the integrity of the barrier when stressed and to allow for quicker and easier installation than would a multi-piece multi-dimensional fire barrier.
Accordingly, the invention described herein addresses this heretofore unmet need.